What Size Solar Panel To Charge 140ah Battery? + Calculator

You need about 200 watts of solar panel to fully charge a 12v 140ah lead-acid battery. Or a 400 watt solar panel to fully charge a 12v 140ah lithium (LiFePO4) battery in a day.

What size solar panel do you need to charge a 140ah lead-acid or lithium battery? Use the calculator given below to find out.

Solar Panel Size Calculator For 140ah Battery

Battery Capacity (Amp-hours)
Ah
Battery Voltage
V
Battery Type
Battery Depth of Discharge (DoD)
%
Charge Controller Type
Desired Charge Time (Peak sun hours)
hours

Note! If you already have a solar panel and want to know how long it will take to charge your battery, use this solar battery charge time calculator.

Calculator Assumptions: 

  • Lead-acid Battery Charge efficiency rate: 85%
  • AGM Battery Charge efficiency rate: 85%
  • Lithium (LiFePO4) Charge efficiency rate: 99%
  • PWM charge controller: 80% efficient
  • MPPT charge controller: 98% efficient
  • Solar Panels Efficiency during peak sun hours: 80% (meaning a 100 watt solar panel will produce 80 watts during peak sun hours, i’ll explain why…)
  • Charge controller is the only load connected with the battery

What Size Solar Panel To Charge 12v 140ah Battery?

To find out what size solar panel you’d need to charge a 140ah battery, enter the following info into the calculator (located at the top of this page)

  • Battery Capacity: in this case, it’ll be 140
  • Battery Volts: is this a 12, 24, or 48 volt battery?
  • Battery Type: Select the battery type, is this a lead-acid, AGM, or lithium-ion (LiFePO4) battery?
  • Battery Depth of discharge DoD: is the percentage of the battery that has been discharged relative to the total battery capacity. for half discharged battery you’d enter 50, (if the battery is fully discharged which you can achieve on lithium battery, ENTER 100)
  • Charge Controller Type: Are you using a PWM or MPPT charge controller to charge the battery? 
  • Desired Charge time (in peak sun hours): How fast would you like to charge your battery or how many peak sun hours your location receives? (keep reading i’ll explain how you can calculate the number of peak sun hours)  

After entering the information, click “Calculate” button to find the required size for a 140ah battery. 

Example 

Suppose you have a 12v 140ah lithium battery with 100% depth of discharge and an MPPT charge controller. You want to recharge your battery in one day (during summer days) and your location receives 7 hours of peak sunlight 

What Size Solar Panel To Charge 140ah Battery
Screenshot from the calculator.

You’d need a 290 watt solar panel to fully charge a 12v 140ah lithium (LiFePO4) battery from 100% depth of discharge in 7 peak sun hours using an MPPT charge controller.

Read the below post to find out how fast you can charge your battery.

Related Post: Guide: Maximum Charging Current & Voltage For 12v Battery

What Are Solar Peak Sun Hours?

Before getting into peak sun hours, let’s first see how solar panels are rated.

“ Solar panels are designed to produce their rated wattage output under standard test conditions – STC ”

STC includes: 

  • 1000 watts per meter square (1kw/m2) of sunlight intensity hitting the solar panels directly
  • 25oC temperature 

So to calculate the sunlight intensity we use peak sun hour as a reference. 

  • 1 peak sun hour = Average of 1kw/meter2 of sunlight intensity for one hour.

This number will depend on the location to location. To calculate how many peak sun hours your city receives use this PVwatt solar calculator.

Step 1: Enter your full address of just a city name & Click GO

Step 2: Click on results

How many peak sun hours in florida?

Now you’d be able to see the total amount of solar radiation your location receives per day (from month to month)

Average Solar Panel Output In Peak Sun Hour 

As we know that solar panels are rated their power under a controlled laboratory environment. But in the real world, there will be some power losses 

These power losses will occur due to various reasons, here are some examples

  • Manufacturer’s output tolerance (+-3%)
  • Dirt and grime on panels (+-5%)
  • DC cable loss (+-3%)
  • Temperature derating (+-10 – 20%)

On average. A solar panel will deliver about 80% of its rated output value in real-world conditions.

This percentage is based on my personal experience with 400 watt solar panels. I collected the 30 days of total output from the solar panels and divide it by that month’s peak sun hours. 

Yes, there’ll be sometimes when you’ll get 100% output from the solar panel but it’s rarely gonna happen and will last for a few minutes 

I have a detailed post about this topic and shared some tips to get the maximum output from your solar panels.

Related Post: Solar Panel Output Calculator – Average Solar Panel Output?

What Size Solar Panel To Charge 12v 140ah Lead-Acid Battery?

Charge TimeCharge Controller TypeRequired Solar Panel
4 peak sun hoursPWM350 watts
5 peak sun hoursPWM280 watts
10 peak sun hoursPWM140 watts
15 peak sun hoursPWM95 watts
20 peak sun hoursPWM70 watts
25 peak sun hoursPWM55 watts
4 peak sun hoursMPPT290 watts
5 peak sun hoursMPPT230 watts
10 peak sun hoursMPPT115 watts
15 peak sun hoursMPPT80 watts
20 peak sun hoursMPPT60 watts
25 peak sun hoursMPPT45 watts

Summary

  • You need around 280 watts of solar panels to charge a 12V 140Ah lead-acid battery from 50% depth of discharge in 5 peak sun hours with a PWM charge controller
  • You need around 230 watts of solar panels to charge a 12V 140Ah lead-acid battery from 50% depth of discharge in 5 peak sun hours with an MPPT charge controller

What Size Solar Panel To Charge 12v 140Ah Lithium (LiFePO4) Battery?

Charge TimeCharge Controller TypeRequired Solar Panel
4 peak sun hoursPWM610 watts
5 peak sun hoursPWM490 watts
10 peak sun hoursPWM245 watts
15 peak sun hoursPWM160 watts
20 peak sun hoursPWM120 watts
25 peak sun hoursPWM100 watts
4 peak sun hoursMPPT510 watts
5 peak sun hoursMPPT410 watts
10 peak sun hoursMPPT200 watts
15 peak sun hoursMPPT135 watts
20 peak sun hoursMPPT100 watts
25 peak sun hoursMPPT80 watts

Summary

  • You need around 490 watts of solar panels to charge a 12V 140Ah lithium battery from 100% depth of discharge in 5 peak sun hours with a PWM charge controller
  • You need around 410 watts of solar panels to charge a 12V 140Ah lithium battery from 100% depth of discharge in 5 peak sun hours with an MPPT charge controller

What Size Solar Panel To Charge 24v 140Ah Lead-Acid Battery?

Charge TimeCharge Controller TypeRequired Solar Panel
4 peak sun hoursPWM700 watts
5 peak sun hoursPWM560 watts
6 peak sun hoursPWM460 watts
10 peak sun hoursPWM280 watts
15 peak sun hoursPWM185 watts
20 peak sun hoursPWM140 watts
4 peak sun hoursMPPT580 watts
5 peak sun hoursMPPT460 watts
6 peak sun hoursMPPT390 watts
10 peak sun hoursMPPT230 watts
15 peak sun hoursMPPT155 watts
20 peak sun hoursMPPT115 watts

Summary

  • You need around 560 watts of solar panels to charge a 24V 140Ah lead-acid battery from 50% depth of discharge in 5 peak sun hours with a PWM charge controller
  • You need around 460 watts of solar panels to charge a 24V 140Ah lead-acid battery from 50% depth of discharge in 5 peak sun hours with an MPPT charge controller

What Size Solar Panel To Charge 24v 140Ah Lithium (LiFePO4) Battery?

Charge TimeCharge Controller TypeRequired Solar Panel
4 peak sun hoursPWM1220 watts
5 peak sun hoursPWM980 watts
6 peak sun hoursPWM815 watts
10 peak sun hoursPWM490 watts
15 peak sun hoursPWM325 watts
20 peak sun hoursPWM250 watts
4 peak sun hoursMPPT1020 watts
5 peak sun hoursMPPT815 watts
6 peak sun hoursMPPT670 watts
10 peak sun hoursMPPT410 watts
15 peak sun hoursMPPT270 watts
20 peak sun hoursMPPT200 watts

Summary

  • You need around 980 watts of solar panels to charge a 24V 140Ah lithium battery from 100% depth of discharge in 5 peak sun hours with a PWM charge controller
  • You need around 815 watts of solar panels to charge a 24V 140Ah lithium battery from 100% depth of discharge in 5 peak sun hours with an MPPT charge controller

How To Choose The Right Size Charge Controller?

The job of the charge controller is to regulate the voltage coming from the solar panels to safely charge the battery and prevent the battery to be overcharged.

To select the right size charge controller according to your solar panel size. Follow these 2 steps

  1. Divide the solar panel rated wattage by battery volts (e.g by 12 for 12v battery and so on…)
  2. Now add an extra 25% to the result value to keep the system safe in case of any fluctuations.
  3. Now the value will be the size of charge controller you’d need with your particular solar panel size to charge the battery.

For Example

let’s suppose you have a 200 watt solar panel and a 12v battery. the calculation will look like this.

200 / 12 = 16.6A
16.6 + 25% or 16.6 * 1.25 = 20.8A 

you’d need a 20A charge controller with a 200 watt solar panel to charge the battery.

PWM Vs MPPT

– PWM Charge Controller

will only decrease the voltage coming from the solar panels and will not increase the amps (current).

which as a result will cause power losses and which makes the PWM charge controllers 20-30% less efficient.

The formula to power is… ( Watts = amps * volts )

Note! a 12v solar panel will produce about 18 volts under direct sunlight conditions... and the amps will be lower.

– MPPT Charge Controller

An MPPT charge controller will not only decrease the voltage coming from the solar panel to charge the battery but will also increase the amps to cover up the losses.

which makes them 98-99% more efficient than a PWM charge controller.

Pro Tip: if your solar panel system is higher then 100 watts then i would suggest using an MPPT charge controller. 

Related Post: How Many Watts Can A Charge Controller Handle?

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I'm an experienced Sales Consultant with a demonstrated history of working in the renewables and environment industry. Skilled in Photography, Customer Service, and Sales.